In the U.S. breast cancer mortality is second only to that of lung cancer. Because of its role in early tumor detection, mammography has come are the most commonly used tool for breast cancer screening, diagnosis and evaluation in the United States. A mammogram is an x-ray image of inner breast tissue that is used to visualize normal and abnormal structures within the breasts. Mammograms provide early cancer detection because they can often show a breast lumps and/or calcifications before they are manually palpable.
While screening mammography is recognized as the most effective method for early detection of breast cancer, the modality has limitations. One problem with mammograms lies in their low specificity; that is it is often difficult to determine whether a detected abnormality is associated with a cancerous or benign lesion. The difficulty arises from the fact that a mammogram is two dimensional representations of a three dimensional structure, and overlapping structures in the compressed breast may confound diagnosis.
Efforts to improve the sensitivity and specificity of breast x-rays have included the development of breast tomosynthesis systems. Breast tomosynthesis is a three-dimensional imaging technology that involves acquiring images of a stationary compressed breast at multiple angles during a short scan. The individual images are then reconstructed into a series of thin, high-resolution slices that can be displayed individually or in a dynamic ciné mode.
Reconstructed tomosynthesis slices reduce or eliminate the problems caused by tissue overlap and structure noise in single slice two-dimensional mammography imaging. Digital breast tomosynthesis also offers the possibility of reduced breast compression, improved diagnostic and screening accuracy, fewer recalls, and 3D lesion localization. Examples of breast tomosynthesis systems are described in U.S. Pat. Nos. 7,245,694 and 7,123,684, commonly owned by the Assignee of this application.
One goal of any x-ray imaging system is to obtain the highest quality image while minimizing the patient dose. When selecting a radiation dose to use for imaging, a balance must be attained between image quality and patient safety. As a result an effort has been made to limit the dose of radiation administered during tomosynthesis imaging. For example, the article “Micro-Calcification Detection in Digital Tomosynthesis Mammography”, by Wheeler et al. describes that a total patient dosing across tomosynthesis projection images in a single scan should be comparable to that administered during a two view mammography.